Two systems, one miscible (hydroxyl-terminated polybutadiene-dioctyl sebacate or HTPB-DOS) and the other immiscible (HTPB-nitroglycerine or HTPB-NG) were simulated by molecular dynamics (MD) simulations with the COMPASS force field for predicting properties of HTPB/plasticizer blends such as the compatibility of polymer binder and plasticizer, the glass transition temperature (T_g) and mechanical properties of polymer/plasticizer blends. Results show that HTPB/DOS is a miscible system but HTPB/NG is not miscible, which can be predicted by comparing the difference in the solubility parameters value (Δδ). The T_g has been determined by the slope of the V-T simulation data, the T_g of HTPB, HTPB/DOS, HTPB/NG is 197.54, 176.30 and 200.03 K respectively. Mechanical properties such as tensile modulus (E), bulk modulus (K) and shear modulus (G) can also be predicted by MD simulations. The mechanical properties can be effectively improved by the addition of DOS plasticizer, which may provide a more flexible mixture, with a lower E, K, G and an increased ductility. Therefore, the method used in this work is a useful tool to provide properties of a given polymer/plasticizer blend. In addition, it is a promising technique to help screen solid propellants and polymer bonded explosive (PBX) formulations before experimental tests.

Key words: HTPB, plasticizer, composite solid propellant, molecular dynamics simulation, compatibility, glass transition temperature, mechanical properties